TWI558748B - Method for producing polarizing film, polarizing plate and method for producing the same - Google Patents

Description

Method for producing polarizing film, polarizing plate and manufacturing method thereof

The present invention relates to a polyvinyl alcohol polymer film (hereinafter, "polyvinyl alcohol" is abbreviated as "PVA"), a method for producing the same, and a polarizing film produced from the PVA polymer film. More specifically, the present invention relates to a PVA-based polymer film which can produce a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization, a method for producing the same, and a long-wavelength region produced by the PVA-based polymer film. A polarizing film with high absorbance and high degree of polarization.

A polarizing plate having light transmission and shielding functions and a liquid crystal having a switching function of light are essential components of a liquid crystal display (LCD). In the early days of development, such as computers and small devices such as watches, the application fields of LCDs in recent years have also been applied to laptop computers, word processors, liquid crystal projectors, car navigation systems, LCD TVs, personal phones, and indoor and outdoor offices. The measuring equipment used and the like exhibit a wide range of expansion. With the expansion of the application field of the LCD as described above, in order to make the polarizing performance higher than that of the conventional product and to improve the color display quality, a polarizing plate of a neutral gray color is required.

Polarizers, in general, are made by using PVA The polymer film is uniaxially stretched and dyed, or dyed and uniaxially stretched, and then fixed with a boron compound (in some cases, two or more operations of dyeing, stretching, and fixing may be simultaneously performed) The resulting polarizing film is bonded to a cellulose triacetate (TAC) film or acetic acid. The composition of a protective film such as a cellulose butyrate (CAB) film.

In order to improve the hue of the polarizing film, the structure of the PVA polymer or the PVA polymer film which is a raw material for the production of the polarizing film, and the manufacturing conditions for producing the polarizing film are mainly discussed. For example, YI is known which is formed by denatured PVA having a polymerization degree of 1500 to 5,000, an ethylene unit content of 1 to 4 mol%, and a 1,2-diol bond amount of 1.4 mol% or less. A polarizing film having a b value of 3 or less produced by uniaxial stretching of a PVA film having a value of 20 or less (see Patent Document 1).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-342322

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2006-188655

[Non-patent literature]

[Non-Patent Document 1] Polymer, 46, 7436-7442 (2005)

[Non-Patent Document 2] Macromolecules, 39 (8), 2921-2929 (2006)

[Non-Patent Document 3] "Physics of Polymers" Springer-Verlag Tokyo Publishing, p.143-154

[Non-Patent Document 4] Journal of Polymer Science : Polymer Physics Edition, Vol. 18, 1343-1359 (1980)

However, as in the conventional polarizing film described in Patent Document 1, a red color may occur at the time of liquid crystal display. The red color visually feels that the polarizing film is red, that is, it is considered to be because the long-wavelength region of the polarizing film (for example, a visible light region of 680 nm or more) has low absorbance. Patent Document 1 does not disclose a means for releasing the red transition while maintaining a high degree of polarization and improving the absorbance in a long wavelength region.

Accordingly, an object of the present invention is to provide a PVA-based polymer film which can produce a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization. Moreover, an object of the present invention is to provide a method for producing a PVA-based polymer film which can smoothly and continuously produce the PVA-based polymer film. Furthermore, it is an object of the present invention to provide a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization.

The absorbance in the long wavelength region of the polarizing film is considered to be changed by changing the crystal structure of the polarizing film. In the polarizing film, the PVA-based polymer film is immersed in water in which various chemicals are dissolved, in one or two or more of the respective steps of dyeing, uniaxial stretching, and fixing treatment. When the PVA-based polymer film is immersed in water, a part of the crystal portion of the PVA-based polymer film is dissolved, and the size of the amorphous portion is increased. That is, PVA in water The crystal structure of the film is different from the crystal structure before immersion in water. In order to increase the absorbance in the long-wavelength region of the polarizing film, the inventors of the present invention have focused on the crystal structure of the PVA-based polymer film in water. Then, it has been found that a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization can be easily obtained by setting a long period of crystals in water which is a scale of the crystal structure to a specific range.

Furthermore, the inventors of the present invention have dried a film forming stock solution containing a PVA-based polymer, and when the film-forming PVA-based polymer film is dried by a wide-angle X-ray diffraction or DSC method, it is found in When the volatility of the film formed of the film-forming raw material solution is about 40% by mass, the PVA-based polymer starts to crystallize, and the film is formed by adjusting the volatilization ratio of the film in the film formation to 40% by mass or less. Under conditions, the long period of crystallinity in water of the obtained PVA-based polymer film can be adjusted. Then, it was found that a film forming apparatus containing a PVA-based polymer was discharged on a first drying roll provided on the most upstream side of the film forming apparatus using a film forming apparatus including a plurality of drying rolls and heat-treating rolls having mutually parallel rotating shafts. The film is formed into a film and dried, and the flow is continued on the lower side of the first drying roll, and the PVA-based polymer film is further dried by the drying roll after the second drying roll, thereby causing the volatilization rate of the film in the film formation. In the specific drying zone of 40% by mass or less, the average value of the temperature of the drying rolls is set to a specific range, and the PVA-based polymer film having a crystal long cycle in a specific range in water can be continuously produced smoothly.

The inventors of the present invention have further repeated discussions based on the above knowledge to complete the present invention. That is, the present invention is:

(1) A PVA-based polymer film whose crystal long period in water It is 14.5~16.0nm.

Also, the present invention is:

(2) A method for producing a PVA-based polymer film, comprising using a film forming apparatus including a plurality of drying rolls and a heat-treating roll having mutually parallel rotating axes, and comprising a PVA-based polymerization on the first drying roll of the film forming apparatus When the PVA-based polymer film is formed by further drying with a drying roll and forming a film of the PVA-based polymer film, T _{1 → 2} represented by the following formula (I) satisfies the following formula. Drying (II), T _1→2 ={T ₁ ×(40-V ₁ )+T ₂ ×(V ₁ -V ₂ )}/(40-V ₂ ) (I) 60≦T _1→2 ≦75 (II) (herein, T ₁ represents the surface temperature (° C.) of the first drying roll, V ₁ represents the volatilization ratio (% by mass) of the film when peeled from the first drying roll, and T ₂ represents the second portion. The average value (°C) of the surface temperature of each drying roller from the drying roller to the drying roller immediately after the heat treatment roller, and V ₂ represents the volatilization rate of the film from the peeling of the drying roller immediately after the heat treatment roller. (% by mass). However, V ₁ is 10 to 30 (% by mass).

Furthermore, the invention is:

(3) A polarizing film produced from the PVA-based polymer film of the above (1).

According to the present invention, there is provided a PVA-based polymer film which is capable of producing a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization. Moreover, according to the present invention, there is provided a method for producing a PVA-based polymer film which can smoothly and continuously produce the PVA-based polymer film. Furthermore, according to the present invention, it provides a long-wavelength region absorption A polarizing film with high luminosity and high degree of polarization.

[Formation of the Invention]

The PVA-based polymer film of the present invention has a crystal long period of 14.5 to 16.0 nm in water. In general, the long period of the crystal refers to an average length of one cycle of the repetition period of the crystal portion and the amorphous portion which are randomly distributed in the film, and the size of the crystal portion and the amorphous portion in the repeating cycle direction. The film formation conditions and the like of the film are changed (see Patent Document 2). In the present invention, since the crystal has a long period of crystal length in the range which is not in the above range, it is a PVA-based polymer film which can produce a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization. From the viewpoint of obtaining a polarizing film having a high absorbance in a long-wavelength region and a high degree of polarization, the crystal has a long period of 14.7 nm or more, more preferably 15.0 nm or more, more preferably 15.1 nm or more, and preferably 15.7 nm or less.

A method of obtaining a long period of a crystal or a thickness of a crystal portion is known as a small-angle X-ray scattering method, and is described in Non-Patent Documents 1 to 4 and the like. The long cycle of crystals in water of the PVA-based polymer film of the present invention is obtained by the small-angle X-ray scattering method. Specifically, in the examples, as described later, small-angle X-ray scattering can be used. The measuring apparatus was obtained by analyzing a PVA-based polymer film in water. Here, as the PVA-based polymer film used for the measurement, those immersed in water (distilled water) at 22 ° C for 24 hours can be used. Impregnating the PVA-based polymer film as described above In the case of water, a part of the crystal portion of the PVA-based polymer film is dissolved and the size of the amorphous portion is increased, but when the time passes, the equilibrium structure is soon reached. Since the equilibrium structure was reached within 24 hours at the slowest in water at 22 ° C, the PVA-based polymer film immersed in water at 22 ° C for 24 hours was used for measurement.

The PVA-based polymer which forms the PVA-based polymer film is, for example, PVA (undenatured PVA) obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester, and grafting a comonomer in a main chain of PVA. a copolymerized denatured PVA-based polymer, a denatured PVA-based polymer produced by saponifying a copolymerized vinyl ester and a conjugated polyvinyl ester of a comonomer, and a part of a hydroxyl group of an undenatured PVA or a denatured PVA-based polymer A so-called polyvinyl acetal resin in which an aldehyde such as formaldehyde, butyraldehyde or benzaldehyde is crosslinked.

When the PVA-based polymer forming the PVA-based polymer film is a denatured PVA-based polymer, the amount of denaturation of the PVA-based polymer is preferably 15 mol% or less, more preferably 5 mol% or less.

Examples of the vinyl ester used for the production of the PVA-based polymer include vinyl acetate, vinyl formate, vinyl laurate, vinyl propionate, vinyl butyrate, trimethyl vinyl acetate, and new Vinyl phthalate, vinyl stearate, vinyl benzoate, and the like. These vinyl esters can be used singly or in combination. Among these vinyl esters, vinyl acetate is preferred from the viewpoint of productivity.

In addition, examples of the comonomer include olefins (α-olefins) having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene, and isobutylene; acrylic acid or a salt thereof; and methyl acrylate. Ethyl acrylate, C Acrylates of n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc. (for example, 1 to 18 alkyl esters of acrylic acid, etc.); methacrylic acid or a salt thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, methyl Methyl acrylate such as n-butyl acrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate Classes (for example, 1 to 18 alkyl esters of methacrylic acid, etc.); acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N,N-dimethyl decylamine, two a acrylamide derivative such as acetone acrylamide, acrylamide sulfonate or a salt thereof, acrylamide propyl dimethylamine or a salt thereof, N-methylol acrylamide or a derivative thereof; Indoleamine, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide sulfonic acid or its salt, methyl propyl A methacrylamide derivative such as amidoxime dimethylamine or a salt thereof, N-methylolmethacrylamide or a derivative thereof; N-vinylformamide, N-vinylacetamide N-vinylguanamines such as N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether Vinyl ethers such as isobutyl vinyl ether, tert-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chloride a vinylidene group such as vinylidene chloride, vinyl fluoride or vinylidene fluoride; an allyl compound such as allyl acetate or allylic chloride; an unsaturated dicarboxylic acid such as maleic acid or itaconic acid; a derivative of a salt or an ester thereof; a vinyl sulfonyl compound such as vinyltrimethoxydecane; isopropenyl acetate Unsaturated sulfonic acid or a derivative thereof. Among these, an α-olefin is preferable, and ethylene is particularly preferable.

The PVA-based polymer forming the PVA-based polymer film has an average polymerization degree of preferably 1,000 or more, more preferably 1,500 or more, and particularly preferably 2,000 or more, from the viewpoints of the polarizing performance and durability of the obtained polarizing film. On the other hand, the upper limit of the average degree of polymerization of the PVA-based polymer is preferably 8,000 or less from the viewpoint of easiness of production of a homogeneous PVA-based polymer film, stretchability, and the like, and is preferably 6,000 or less. good.

Here, the "average degree of polymerization" of the PVA-based polymer in the present specification means the average degree of polymerization measured according to JIS K6726-1994, and the saponification of the PVA-based polymer is carried out, and after purification, it is measured in water at 30 ° C. The ultimate viscosity is determined.

The degree of saponification of the PVA-based polymer forming the PVA-based polymer film is preferably 95.0 mol% or more, more preferably 98.0 mol% or more, and 99.0 mol%, from the viewpoints of the polarizing performance and durability of the obtained polarizing film. The above is especially good, 99.3% of the above is the best.

Here, the "saponification degree" of the PVA-based polymer of the present specification means the total number of moles of a structural unit (typically a vinyl ester unit) obtained by converting into a vinyl alcohol unit by saponification energy, and a vinyl alcohol unit. The proportion of the molar number of the vinyl alcohol unit (% by mole). The degree of saponification of the PVA-based polymer can be measured in accordance with the description of JIS K6726-1994.

In addition to the PVA-based polymer, the PVA-based polymer film may further include a plasticizer, a surfactant, and the like, which will be described later, as an example of the production method of the present invention. Various additives and the like.

The thickness of the PVA-based polymer film is not particularly limited, but is preferably 5 to 80 μm when used as a polarizing film for initial use. A more suitable thickness is 20 to 80 μm. When the thickness of the PVA-based polymer film is equal to or less than the above-described upper limit, the drying of the PVA-based polymer film can be performed more quickly, and the thickness of the PVA-based polymer film can be more effectively suppressed. Breakage of the film produced during uniaxial stretching to produce a polarizing film.

The width of the PVA-based polymer film is not particularly limited. However, in recent years, the liquid crystal television or the monitor has a large screen. Therefore, in order to be effectively used for such applications, the width is preferably 2 m or more, and more preferably 3 m or more. More than 4m is ideal. Further, when the polarizing plate is produced by a real production machine, if the width of the film is too large, uniform uniaxial stretching is difficult, and therefore the width of the PVA polymer film is preferably 8 m or less. The length of the PVA-based polymer film is not particularly limited, and may be, for example, 50 to 30000 m.

The retardation value of the PVA-based polymer film is not particularly limited, but the phase difference in the width direction of the polarizing film obtained as the retardation value is smaller tends to be improved, so that it is preferably 100 nm or less. This retardation value can be measured by the method described later in the examples.

The PVA-based polymer film preferably has a mass swelling degree of 180 to 250%, more preferably 185 to 240%, and particularly preferably 190 to 230%. When the mass swellability of the PVA-based polymer film is at least the above lower limit, the stretching becomes easy, and the polarizing film having a good polarizing property tends to be easily changed. On the other hand, the mass swellability is equal to or less than the upper limit. Stretch In the case where the step is improved, the production of the highly durable polarizing film tends to be easy to change.

The term "mass swellability" as used herein refers to the percentage of the mass obtained by immersing the PVA-based polymer film in distilled water at 30 ° C for 30 minutes, and dividing the mass obtained by drying at 105 ° C for 16 hours after immersion, specifically In the examples, it can be measured by the method described later.

The method for producing the PVA-based polymer film of the present invention is not particularly limited. However, according to the production method of the present invention described below, the PVA-based polymer film of the present invention can be continuously produced smoothly.

In other words, in the production method of the present invention for producing a PVA-based polymer film, a plurality of drying rolls having a rotation axis parallel to each other are used (from the uppermost flow side toward the downstream side, which are sequentially referred to as a first drying roll, 2 drying roll...) The film forming apparatus of the heat treatment roll, the film forming raw material containing the PVA type polymer is discharged into a film form on the first drying roll of the film forming apparatus, and dried, and then dried by a drying roll. When the PVA-based polymer film is formed into a film, T _{1 → 2} represented by the following formula (I) is dried by satisfying the following formula (II).

T _1→2 ={T ₁ ×(40-V ₁ )+T ₂ ×(V ₁ -V ₂ )}/(40-V ₂ ) (I)

60≦T _1→2 ≦75 (II)

In the above formulae (I) and (II), T ₁ represents the surface temperature (° C.) of the first drying roll, and V ₁ represents the volatilization ratio (% by mass) of the film when peeled off from the first drying roll, and T ₂ represents The average value (°C) of the surface temperatures of the respective drying rolls from the second drying roll to the drying roll immediately after the heat treatment roll, and V ₂ represents the film from the peeling of the drying roll immediately after the heat treatment roll Volatile fraction (% by mass). Then, V ₁ is from 10 to 30 (% by mass).

As described above, the inventors have found that when the volatility of the film formed of the film forming stock solution is about 40% by mass, the PVA-based polymer starts to crystallize, and the volatility of the film in the film formation is adjusted as described above. In the film forming conditions at 40% by mass or less, the crystal long period in water of the obtained PVA polymer film can be adjusted, but the average value of the temperature of the drying roll which is one of the film forming conditions is shown. The surface temperature (T ₁ ) including the first drying roll, the volatile matter ratio (V ₁ ) of the film when peeled from the first drying roll, and the surface temperature of each drying roll from the second drying roll to the last drying roll are used. The average value (T ₂ ) and the above formula (I) of the volatilization ratio (V ₂ ) of the film when peeled off from the last drying roll.

Furthermore, the above formula (I) is derived as follows. In detail, the film forming stock solution containing the PVA-based polymer is discharged into a film form on the first drying roll having a surface temperature T ₁ (° C.), and dried on the first drying roll until the film is volatilized. When the V ₀ (% by mass) is V ₁ (% by mass), the film is peeled off from the first drying roll, and then the plurality of drying rolls after the second drying roll (the average of the surface temperatures of the drying rolls) Further drying for T ₂ (°C)), and when the volatilization ratio of the film is V ₂ (% by mass), from the case where the last drying roll located directly in front of the heat treatment roll is peeled off, the volatile matter ratio V ₀ (quality) %) The average value _Tever (°C) of the surface temperature of the drying roll in the drying zone to the volatile fraction V ₂ (% by mass) can be expressed by the following formula (I').

T _Ave = T ₁ × (V ₀ - V ₁ ) / (V ₀ - V ₂ ) + T ₂ × (V ₁ - V ₂ ) / (V ₀ - V ₂ ) (I')

Here, as described above, in order to adjust the film formation conditions when the volatility of the film in the film formation is 40% by mass or less, if V ₀ of the above formula (I') is V ₀ = 40 (% by mass), T _Ave will become the equivalent of the formula (I), T _{1 → 2.}

In the production method of the present invention, the above formula (II) is satisfied, that is, the value of T _{1 → 2} of the above formula (I) is required to be in the range of 60 to 75. In the range of T _{1 → 2} , the aforementioned PVA-based polymer film having a crystal long period in a specific range in water can be continuously produced smoothly. According to the PVA polymer film which can be more easily produced, T _{1 → 2 is} preferably 61 or more, 63 or more is preferable, 64 or more is more preferable, 64.5 or more is particularly preferable, 65 or more is optimal, and T _{1 → 2} is 72 or less. Preferably, it is more preferably 69.5 or less.

In the production method of the present invention, a film forming apparatus including a plurality of drying rolls and heat treatment rolls having parallel axes of rotation are used, and a film forming raw liquid containing a PVA polymer is discharged onto the first drying roll of the film forming apparatus. The film was dried and dried on the downstream side of the first drying roll, and further dried by a drying roll after the second drying roll to form a PVA-based polymer film. In the film forming apparatus, the number of drying rolls is preferably 3 or more, more preferably 4 or more, and particularly preferably 5 to 30.

The plurality of drying rolls are preferably formed of a metal such as nickel, chromium, copper, iron, stainless steel or the like, and in particular, the surface of the drying roll is preferably formed of a metal material which is not easily corroded and has a specular gloss. Moreover, in order to improve the durability of the drying roll, it is more preferable to use a plating roll or a combination of two or more nickel layers, a chromium layer, a nickel/chromium alloy layer, and the like.

Regarding the heating direction when the film is dried from the first drying roll to the last drying roll located directly in front of the heat treatment roll, the film can be further uniformly dried, and in any part of the film, the first drying is performed. The film surface that is in contact with the roller (hereinafter referred to as "the first drying roller contact surface") and the film surface that is not in contact with the first drying roller (hereinafter sometimes referred to as "the first drying roller non-contact surface") are From the first drying roll to the final drying It is preferred that each of the drying rolls until the rolls are alternately dried.

When the surface temperature of the plurality of drying rolls is too high, there is a tendency that heat treatment is effected in one part of the PVA-based polymer film, and the crystal structure becomes uneven, and if it is too low, it is difficult to dry efficiently. The tendency is preferably in the range of 30 to 95 ° C, more preferably in the range of 40 to 85 ° C, and particularly preferably in the range of 60 to 75 ° C. More specific surface temperatures of the individual drying rolls are preferably as described later.

When the film forming stock solution containing the PVA-based polymer is discharged into a film form on the first drying roll of the film forming apparatus, for example, a T-slot die, a hopper plate, an I-die, a lip-mouth coating die, or the like is used. In the known film-like discharge device (film-like casting device), the film-forming stock solution containing the PVA-based polymer may be discharged (cast) onto the first drying roll to form a film.

The film forming stock solution containing the PVA polymer film can be prepared by mixing a PVA polymer with a liquid medium to form a solution, and melting a PVA polymer pellet containing a liquid medium or the like into a molten liquid or the like.

As the liquid medium to be used at this time, for example, water, dimethyl hydrazine, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylenediamine, diethylenetriamine may be mentioned. The liquid medium may be used singly or in combination of two or more. Among these, it is preferred to use water, dimethyl hydrazine, or a mixture of the two, and it is more preferable to use water in particular.

Adding a plasticizer to the film forming solution from the viewpoint of promoting the dissolution or melting of the liquid medium of the PVA-based polymer, improving the processability of the PVA-based polymer film, and improving the stretchability of the PVA-based polymer film obtained. More ideal.

As the plasticizer, a polyhydric alcohol is preferably used, and examples thereof include ethylene glycol, glycerin, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane. One type of these plasticizers may be used alone or two or more types may be used in combination. Among these, one or two or more of glycerin, diglycerin, and ethylene glycol are preferable from the viewpoint of improving the stretchability.

The amount of the plasticizer added is preferably from 0 to 30 parts by mass based on 100 parts by mass of the PVA-based polymer. When the amount of the plasticizer added is 30 parts by mass or less based on 100 parts by mass of the PVA-based polymer, the obtained PVA-based polymer film does not become too soft, and the deterioration of handleability can be suppressed. The amount of the plasticizer added is 3 parts by mass or more based on 100 parts by mass of the PVA-based polymer, from the viewpoint of the handleability of the obtained PVA-based polymer film or the PVA-based polymer film which can be produced more smoothly. More preferably, it is more preferably 5 parts by mass or more, more preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and most preferably 15 parts by mass or less.

It is preferable to add a surfactant to the film forming stock solution from the viewpoint of improving the peeling property of the drying roll from the production of the PVA-based polymer film, the handleability of the obtained PVA-based polymer film, and the like. The kind of the surfactant is not particularly limited, but an anionic surfactant or a nonionic surfactant is preferably used.

As the anionic surfactant, for example, an anionic surfactant such as a carboxylic acid type such as potassium laurate or a sulfate type such as octyl sulfate or a sulfonic acid type such as dodecylbenzenesulfonate is suitable.

Further, as the nonionic surfactant, for example, an alkyl ether type such as an alkyl ether type such as polyoxyethylene oleyl ether or a polyphenylene octyl phenyl ether or the like An alkyl ester type such as oxyethylene laurate or an alkylamine type such as polyoxyethylene lauryl amine ether, a polyalkylene laurate or the like, or a polyoxyethylene polyoxypropylene ether. Nonionic surfactants such as propylene glycol ether type, lauric acid diethanolamine, oleic acid diethanolamine, etc., such as allylic phenylamine type and polyoxyalkylallyl phenyl ether, etc. appropriate. These surfactants may be used alone or in combination of two or more.

The amount of the surfactant to be added is preferably 0.01 to 1 part by mass, more preferably 0.02 to 0.5 part by mass, and particularly preferably 0.05 to 0.3 part by mass, based on 100 parts by mass of the PVA polymer. When the amount of the surfactant to be added is 0.01 parts by mass or more based on 100 parts by mass of the PVA-based polymer, the effect of improving the film forming property and the peeling property can be easily exhibited. On the other hand, the content can be suppressed by 1 part by mass or less. The active agent dissolves on the surface of the film to cause agglomeration, and the deterioration of handleability can be suppressed.

In the film forming stock solution, in addition to the above-mentioned components, various additives may be contained, for example, a stabilizer (antioxidant, ultraviolet absorber, heat stabilizer, etc.), a phase solvent, an anti-caking agent, a flame retardant, and an anti-blocking agent. Electrostatic agents, lubricants, dispersants, fluidizers, antibacterial agents, and the like. These additives may be used alone or in combination of two or more.

The volatilization ratio of the film forming stock solution used for the production of the PVA-based polymer film is usually 40% by mass or more, preferably 50 to 90% by mass, more preferably 60 to 80% by mass. When the volatilization rate of the film-forming raw material solution is too low, the viscosity of the film-forming raw material solution becomes too high, and filtration or defoaming becomes difficult, and the film formation itself becomes difficult. On the other hand, if the volatilization rate of the film-forming stock solution is too high, the viscosity becomes too low and the PVA-based polymer is thin. The case of the uniformity of the thickness of the film.

Here, the "volatility of the film forming solution" referred to in the present specification means a volatile matter ratio obtained by the following formula (III).

Volatile fraction (% by mass) of the film forming solution solution = {(Wa - Wb) / Wa} × 100 (III) (here, Wa represents the mass (g) of the film forming stock solution, and Wb represents the system of Wa (g). The mass (g) of the film stock solution after drying for 16 hours in an electric dryer at 105 ° C.)

When the PVA-based polymer film of the present invention is more smoothly produced by drying on the first drying roll which is formed into a film-forming film forming solution, the surface temperature (T ₁ ) of the first drying roll is 60 to 90. °C is preferred. Moreover, the roll surface temperature (T ₁ ) of the first drying roll is preferably 65° C. or more, more preferably 70° C. or more, and more preferably 85° C. or less, and 80° C. or less, from the viewpoint of ensuring more stable productivity. Good, the best below 75 °C.

The drying on the first drying roll which discharges the film forming film forming solution may be performed only by heating from the first drying roll, but the first drying roll is used from the viewpoints of uniform drying property, drying speed, and the like. At the same time as heating, hot air is sprayed on the non-contact surface of the first drying roll, and it is preferable to apply heat from both sides of the film to perform drying.

When hot air is sprayed on the non-contact surface of the first drying roll of the film on the first drying roll, it is preferable to spray hot air of 1 to 10 m/sec in the entire area of the non-contact surface of the first drying roll, and the spraying wind speed is 2 to 8 m. The hot air of /second is more ideal, and the hot air with a wind speed of 3~8m/sec is ideal. When the wind speed of the hot air sprayed on the non-contact surface of the first drying roll is too small, condensation occurs in water vapor or the like during drying on the first drying roll, and the water droplets are dropped on the film. The PVA-based polymer film obtained in the end is likely to cause defects. On the other hand, when the wind speed of the hot air sprayed on the non-contact surface of the first drying roll is too large, there is a problem in that the PVA-based polymer film finally obtained is uneven in thickness, and the occurrence of dye spots is caused.

From the viewpoints of drying efficiency, uniformity of drying, etc., the temperature of hot air sprayed on the non-contact surface of the first drying roll of the film is preferably 50 to 150 ° C, more preferably 70 to 120 ° C, and particularly ideal at 80 to 95 ° C. . When the temperature of the hot air sprayed on the non-contact surface of the first drying roll of the film is too low, condensation of water vapor or the like may occur, and water droplets may fall on the film, and the PVA-based polymer film finally obtained may be defective. On the other hand, when the temperature is too high, dry spots are generated along the wind direction of the hot air, and the PVA-based polymer film finally obtained may have uneven thickness.

Further, the dew point temperature of the hot air sprayed on the non-contact surface of the first drying roll of the film is preferably 5 to 20 ° C, more preferably 10 to 15 ° C. When the dew point temperature of the hot air sprayed on the non-contact surface of the first drying roll of the film is too low, drying efficiency, uniform drying property, and the like are liable to lower. On the other hand, when the dew point temperature is too high, foaming is likely to occur.

The method for spraying hot air on the non-contact surface of the first drying roll of the film is not particularly limited, and any non-contact surface of the first drying roll which can spray the hot air having uniform wind speed and uniform temperature on the film can be used, preferably A method of uniformly spraying the whole, wherein a nozzle method, a rectifying plate method, or a combination thereof is preferably employed. The spraying direction of the hot air on the non-contact surface of the first drying roll of the film may be a direction facing the non-contact surface of the first drying roll, or may be a circumferential shape of the non-contact surface of the first drying roll of the film. Direction (almost along the circumference of the roll surface of the first drying roll) Direction), or may be in a direction other than the foregoing.

Further, when the film on the first drying roll is dried, it is preferable to evacuate the hot air sprayed from the volatile component generated by the film by drying. The method of exhausting is not particularly limited, but an exhaust method in which wind speed unevenness and temperature unevenness of hot air which does not spray on the non-contact surface of the first drying roll of the film are not preferable is preferable.

The peripheral speed (S ₁ ) of the first drying roll is preferably from 5 to 30 m/min from the viewpoints of uniform drying property, drying speed, productivity of the PVA-based polymer film, and the like. When the peripheral speed (S ₁ ) of the first drying roll is less than 5 m/min, the productivity is lowered, and the stretchability of the obtained PVA-based polymer film tends to decrease. On the other hand, when the peripheral speed (S ₁ ) of the first drying roll exceeds 30 m/min, the thickness of the cut surface tends to increase when the both ends of the film are cut.

The film-forming stock solution is discharged onto the first drying roll, and is dried on the first drying roll, and the volatile matter ratio of the film (volatility of the film when peeled from the first drying roll: V ₁ (mass) When %)) is 10 to 30% by mass, it is peeled off from the first drying roll. When the volatilization ratio (V ₁ ) of the film at the time of peeling from the first drying roll is less than 10% by mass, the film passing through the first drying roll becomes hard, and the passability of the step is lowered, which is not preferable. On the other hand, when the volatilization ratio (V ₁ ) of the film at the time of peeling from the first drying roll exceeds 30% by mass, drying on the contact surface side of the first drying roll is insufficient, and peeling failure is likely to occur. From the above viewpoint, the volatilization ratio (V ₁ ) of the film when peeled off from the first drying roll is preferably 15% by mass or more, more preferably 18% by mass or more, particularly preferably 20% by mass or more, and 29% by mass or less. Preferably, it is more preferably 28% by mass or less, and particularly preferably 27% by mass or less.

Here, the "volatility of the film" in the present specification means a volatile matter ratio obtained by the following formula (IV).

V (% by mass) = {(Wc - Wd) / Wc} × 100 (IV) (here, V represents the volatilization ratio (% by mass) of the film, and Wc represents the mass (g) of the sample taken from the film, Wd The mass (g) when the sample Wc (g) was placed in a vacuum dryer having a temperature of 50 ° C and a pressure of 0.1 kPa or less for 4 hours.

The film is dried on the first drying roll until the film having the above volatilization ratio (V ₁ ) is peeled off from the first drying roll. This time, it is preferable to make the first drying roll non-contact surface of the film face the second drying roll. 2 The drying roller dries the film.

The ratio (S ₂ /S ₁ ) of the peripheral speed (S ₂ ) of the second drying roll to the peripheral speed (S ₁ ) of the first drying roll is preferably 1.005 to 1.150, more preferably 1.010 to 1.100. When the ratio (S ₂ /S ₁ ) is less than 1.005, peeling from the first drying roll becomes difficult, and the film may be broken. Moreover, when the ratio (S ₂ /S ₁ ) exceeds 1.150, it tends to be difficult to produce the intended PVA-based polymer film.

According to the PWA-based polymer film of the present invention, the average value (T ₂ ) of the surface temperatures of the respective drying rolls from the second drying roll to the last drying roll directly in front of the heat-treating roll can be more smoothly produced (each drying is performed) The average value of the surface temperature of the roll is preferably from 50 to 75 °C. In particular, from the viewpoint of ensuring stable productivity, the average value (T ₂ ) is preferably 55 ° C or more, more preferably 60 ° C or more, and more preferably 70 ° C or less, and more preferably 68 ° C or less.

The volatility (V ₂ ) of the film at the time of peeling from the last drying roll is also based on the volatility (V ₁ ) of the film at the time of peeling from the first drying roll, etc., but the present invention can be more smoothly produced. In the PVA-based polymer film, the volatile fraction (V ₂ ) is preferably 1% by mass or more, more preferably 3% by mass or more, more preferably 15% by mass or less, even more preferably 10% by mass or less, and 9% by mass or less. good.

In order to produce the PVA-based polymer film of the present invention more smoothly, the ratio (S _L /S ₁ ) of the peripheral speed (S _L ) of the last drying roll to the peripheral speed (S ₁ ) of the first drying roll is 0.975. ~1.150 is better, 0.980~1.100 is better. When the ratio (S _L /S ₁ ) is less than 0.975, the film becomes liable to collapse between the drying rolls, and when the ratio (S _L /S ₁ ) exceeds 1.150, it is difficult to manufacture the PVA-based polymer film as a target. Propensity.

The film dried as described above was peeled off from the last drying roll, and heat-treated by a heat treatment roll on the downstream side thereof. The number of heat treatment rolls may be one or more, and any one may be used.

The surface temperature of the heat treatment roll is preferably 90 ° C or higher, more preferably 95 ° C or higher, and particularly preferably 100 ° C or higher, in accordance with the PVA polymer film which is moderately crystallized and has excellent hot water resistance. Moreover, from the viewpoint of the stretchability of the PVA-based polymer film obtained by the lift, the surface temperature of the heat-treating roll is preferably 150 ° C or less, more preferably 130 ° C or less, and particularly preferably 120 ° C or less.

The heat treatment time is not particularly limited, but the PVA-based polymer film of the present invention can be more smoothly produced in a range of from 3 to 60 seconds, more preferably in the range of from 5 to 30 seconds.

The volatilization rate of the film before heat treatment is generally the same as the value of V ₂ described above. In the heat treatment, the volatilization rate of the film may or may not vary, for example, it may be lower than the value of V ₂ in the heat treatment. In the production method of the present invention, the average value (T ₂ ) of the surface temperatures of the respective drying rolls from the second drying roll to the last drying roll is preferably 50 to 75 ° C as described above, in order to become the average value ( T ₂ ), the surface temperature of each of the drying rolls from the second drying roll to the last drying roll is also preferably in the range of 50 to 75 ° C, and when the surface temperature of the heat-treating roll is 90 ° C or more as described above, Each of the drying rolls and the heat treatment rolls can be clearly distinguished.

The film forming apparatus described above may have a hot air drying device, a humidity control device, or the like as needed, and for example, a humidity control treatment may be applied after the heat treatment. Further, both ends (ears) of the film can be cut as needed.

The PVA-based polymer film finally obtained by the above-described series of processes preferably has a volatility of from 1 to 5% by mass, more preferably from 2 to 4% by mass. The obtained PVA-based polymer film is preferably wound into a roll shape with a predetermined length.

In order to produce a polarizing film from the PVA-based polymer film of the present invention, for example, a PVA-based polymer film may be dyed, uniaxially stretched, fixed, dried, and heat-treated as needed. The order of dyeing and uniaxial stretching is not particularly limited, and the dyeing treatment may be performed before the uniaxial stretching treatment, or the dyeing treatment may be performed simultaneously with the uniaxial stretching treatment, or the dyeing treatment may be performed after the uniaxial stretching treatment. . Further, the steps of uniaxial stretching, dyeing, and the like may be repeated a plurality of times. In particular, when the uniaxial stretching is divided into two or more stages, uniform stretching can be easily performed, which is preferable.

As the dye used for dyeing the PVA-based polymer film, iodine or a dichroic organic dye can be used (for example, Direct Black 17, 19, 154; Direct Brown 44, 106, 195, 210, 223; Direct Red 2, 23, 28, 31, 37, 39, 79, 81, 240, 242, 247; DirectBlue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; DirectViolet 9, 12, 51, 98; DirectGreen 1, 85; DirectYellow 8, 12, 44, 86, 87; DirectOrange 26, 39, 106, 107 and other dichroic dyes). These dyes may be used alone or in combination of two or more. The dyeing is usually carried out by immersing the PVA-based polymer film in a solution containing the aforementioned dye, but the treatment conditions or treatment methods are not particularly limited.

The uniaxial stretching of the PVA-based polymer film in the direction of flow (MD) or the like can be carried out by either a wet stretching method or a dry heat stretching method, but the properties of the obtained polarizing film and From the viewpoint of quality stability, the wet stretching method is preferred. The wet stretching method is a method of stretching a PVA-based polymer film in an aqueous solution containing various components such as pure water, an additive, or an aqueous medium, or an aqueous dispersion in which various components are dispersed; Specific examples of the uniaxial stretching method by the stretching method include a method of uniaxial stretching in warm water containing boric acid, a method of uniaxial stretching in a solution containing the dye, or a fixed treatment bath to be described later. Further, the PVA-based polymer film after water absorption can be used for uniaxial stretching in air, and may be uniaxially stretched by other methods.

The stretching temperature at the time of uniaxial stretching is not particularly limited, but it is preferably 20 to 90 ° C, more preferably 25 to 70 ° C, and particularly preferably 30 to 65 ° C in wet stretching. For the temperature and dry heat drawing, it is preferred to use a temperature in the range of 50 to 180 °C.

From the viewpoint of polarizing performance, the film is preferably stretched as much as possible immediately before the cutting, and the stretching ratio of the uniaxial stretching treatment (the total stretching ratio when uniaxially stretching in multiple stages), specifically 4 More than Good, more than 5 times better, more than 5.5 times better. The upper limit of the stretching ratio is not particularly limited as long as the film is not broken, but it is preferably 8.0 times or less for uniform stretching.

In the production of a polarizing film, in order to reinforce the adsorption of the dye to the uniaxially stretched film, a fixing treatment is often performed. In the fixing treatment, a method of immersing a film in a treatment bath in which boric acid and/or a boron compound is added is generally employed. At this time, an iodine compound may be added to the treatment bath as needed.

The film subjected to the uniaxial stretching treatment, the uniaxial stretching treatment, and the fixing treatment is preferably subjected to a drying treatment (heat treatment). The drying treatment (heat treatment) has a temperature of 30 to 150 ° C, particularly preferably 50 to 140 ° C. When the temperature of the drying treatment (heat treatment) is too low, the dimensional stability of the obtained polarizing film is likely to be lowered. On the other hand, when it is too high, the polarization performance is likely to be lowered due to decomposition of the dye or the like.

According to the PVA-based polymer film of the present invention, a polarizing film having a high absorbance in a long wavelength region and which is less likely to cause red color can be produced. As an index indicating the absorbance in the long-wavelength region of the polarizing film, the absorbance at a measurement wavelength of 700 nm at a specific transmittance can be employed. In the polarizing film produced by the PVA-based polymer film of the present invention, the absorbance (Abs) at a measurement wavelength of 700 nm of a transmittance of 43.5% is preferably 3.0 or more, and more preferably 3.1 or more. The absorbance (Abs) can be obtained by the method described later in the examples.

As the polarizing plate, a protective film which is optically transparent and has mechanical strength can be bonded to both surfaces or one surface of the polarizing film obtained as described above. As a protective film in this case, triacetate fiber is used. A TAC film, a cellulose acetate butyrate (CAB) film, an acrylic film, a polyester film, or the like. Further, as the adhesive for bonding the protective film, a PVA-based adhesive or a urethane-based adhesive is generally used, and a PVA-based adhesive is preferably used.

The polarizing plate obtained as described above can be bonded to a glass substrate after being coated with an adhesive such as acrylic, and used as a component of a liquid crystal display device. When the polarizing plate is bonded to the glass substrate, a phase difference film, a viewing angle lifting film, a brightness enhancement film, or the like may be bonded at the same time.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples.

In the following examples and comparative examples, the volatilization ratio of the film forming solution; the volatilization ratio of the film; the surface temperature of the drying roll and the heat treatment roll; the long period of crystal length in the water of the PVA type polymer film, the crystal thickness and the non- Crystal thickness; retardation value of PVA-based polymer film; mass swelling degree of PVA-based polymer film; and optical properties of polarizing film were measured by the following methods.

(1) Volatile fraction of film forming stock solution

A heat-resistant container made of a film-forming stock solution of about 10 g was placed in a heat-resistant container, and the heat-resistant container was sealed, and the mass Wa (g) of the film-forming stock solution from which the package was removed was measured up to four decimal places. Next, the film forming stock solution was placed in an electric heat dryer having a temperature of 105 ° C in each heat-resistant container, and dried for 16 hours in a state in which the lid of the heat-resistant container was opened, and then the mass Wb (g) of the film-forming stock solution from which the package was removed was measured until 4 digits below the decimal point. From the obtained quality Wa and Wb, according to the former The volatility (% by mass) of the film forming solution was determined by the above formula (III).

(2) Volatile fraction of the film

Regarding between the adjacent rolls (between the first drying roll and the second drying roll, or between the last drying roll and the heat-treating roll), the center portion of the width direction (TD) of the film between the passing rolls is cut. About 5 g of the film sample, or about 5 g of the film sample cut from the center of the width direction (TD) of the obtained PVA film, was placed in a heat-resistant container made of glass and sealed, and the quality of the film from which the package was removed was measured. Wc(g) is up to 4 digits below the decimal point. Next, the film was placed in a vacuum dryer having a temperature of 50 ° C and a pressure of 0.1 kPa or less in each heat-resistant container, and dried in a state in which the lid of the heat-resistant container was opened for 4 hours, and then the quality of the film from which the package was removed was measured (W). Up to 4 digits below the decimal point. From the obtained masses Wc and Wd, the volatilization ratio V (% by mass) of the film was determined from the above formula (IV).

(3) Surface temperature of the drying roller and the heat treatment roller

The measurement point is set to 5 points in the width direction of the drying roller or the heat treatment roller. Specifically, the position in the center in the width direction is taken as the measurement point in the center, and two points are taken at intervals of 10 cm on both sides thereof, and the measurement points that are combined into five are arranged on a straight line. Then, using a non-contact surface thermometer, the roll surface temperature (° C.) at each point was measured up to one decimal place. The average value of the roll surface temperatures of the respective points was taken as the surface temperature of each of the drying rolls or the heat treatment rolls.

(4) Crystal long period, crystal thickness and amorphous thickness of PVA polymer film in water

In the present invention, with reference to the above documents, the crystal long period, the crystal thickness, and the amorphous thickness are obtained in a state where the sample is immersed in water. Here, crystallization The long period, the crystal thickness (thickness of the crystal portion), and the amorphous thickness (thickness of the amorphous portion) are derived from the correlation function K(z) as described in detail below. Further, the correlation function K(z) is given by Fourier transforming the scattering function obtained by the small angle X-ray scattering method, and is defined as in the formula (V).

The crystal long period, crystal thickness, and amorphous thickness in water in the central portion of the width direction (TD) of the PVA film obtained in the following examples or comparative examples are determined by the following "Measurement Method of "1" Crystal Structure" And the method shown in the item of "analysis method of "2" crystal structure" was obtained. Further, in consideration of the difference in measurement, in the five different places in the flow direction (MD) of the central portion in the width direction (TD) of the PVA film, the crystal long period, the crystal thickness, and the amorphous thickness are determined, and The five values obtained by the long period of crystal length, the thickness of crystal and the thickness of amorphous are averaged, respectively, as the long period of crystal in water of PVA film, the crystal thickness in water and the amorphous thickness in water. .

Determination of the crystal structure of "1":

The central portion in the width direction (TD) of the PVA film obtained in the following examples or comparative examples was cut into a plurality of film samples having a size of MD (flow direction) × TD = 2 cm × 1 cm. The film samples were overlapped in the same direction until the thickness became about 1 mm so that bubbles did not enter between them, and were immersed in distilled water having a mass ratio of about 1000 times of about 22 times for 24 hours. The measurement was carried out by using a nano-scale X-ray structure evaluation apparatus (small-angle X-ray scattering measurement apparatus) "Nano Viewer" (manufactured by Rigaku Co., Ltd.) to measure the transmission in the vertical direction. .

Furthermore, the structure of the cartridge is a polyimide film having a thickness of 7.5 μm. The window material on the incident light side and the reflected light side was used, and the interval between the window materials was set to about 1.5 mm, so that the measured sample was sealed in water. When the cartridge is used, the sample can be placed in water in a generally measured configuration of the apparatus described above.

[Measurement conditions]

X-ray: CuKα line

Wavelength: 0.15418nm

Output: 40kv-20mA

First slit: 0.4mm

Second slit: 0.2mm

Third slit: 0.45mm

Detector: image plate Size: 127mm × 127mm

Pixel size: 50μm × 50μm

Camera length: 960mm

X-ray exposure time: 2 hours

Ambient temperature: 22 ° C

Analytical method for the crystal structure of "2":

First, dark noise generated based on the dark current of the detector is subtracted from each measurement data. The measurement of the dark noise data was performed in an arrangement different from the measurement of the sample without X-ray irradiation.

Further, in the measurement by the small-angle X-ray scattering method, since the scattering of the PVA film overlaps with the device from the slit or the like, the air passing through the X-ray passage portion, and the scattering of the water inside the cartridge, it is necessary to Since the scattering is corrected as a background, in the present invention, the scattering intensity obtained by measuring the sample is additionally calculated from the above-described scattering intensity, and the scattering intensity obtained by measuring the sample is subtracted and corrected.

Furthermore, the scattering intensity image measured by the two-dimensional detector integrates the scattering intensity of the scattering vector q with the azimuthal direction, and derives the relationship between the scattering vector q and the one-dimensional contour of the scattering intensity I(q) to obtain a scattering curve. . Further, the scattering intensity in the region where q is 2 nm ^-1 or more is fitted by the least square method using the constant c, and the obtained constant c is used as a reference, and the self-scattering intensity is subtracted. Further, the difference between the data corrected by the fixed number c is the main cause of the error at the time of obtaining the correlation function K(z), and the least squares fitting is performed using the Gaussian function. The correlation function K(z) is derived using Fourier transform using the scattering curve obtained as described above.

The z coordinate value of the maximum point of the correlation function K(z) derived as described above is taken as the crystal long period. Further, a value calculated from the intersection of the straight line passing through the slope 0 of the minimum point of the correlation function K(z) and the straight line approximated by the region where z is small is defined as the crystal thickness. Specifically, in the present invention, the straight line passing through the slope 0 of the minimum point of the correlation function K(z) is obtained and the correlation function K(z) for the range of 1.0 to 2.5 nm for z is approximated by the least squares method. The intersection of the straight lines, and the z coordinate value of the intersection is taken as the crystal thickness. Further, the value obtained by subtracting the crystal thickness from the long period of the crystal was calculated as the amorphous thickness.

(5) Blocking value of PVA polymer film

The PVA film obtained in the following examples or comparative examples was subjected to "KOBRA-WFD" (manufactured by Oji Scientific Instruments Co., Ltd., measuring wavelength: 590 nm), and the retardation value was measured over the entire range in the width direction at a pitch of 50 mm. The average value was taken as the retardation value of the PVA film.

(6) Quality swelling degree of PVA polymer film

The PVA film obtained in the following examples or comparative examples was cut into About 1.5 g was immersed in 1000 g of distilled water at 30 ° C for 30 minutes, and after immersing for 30 minutes, the PVA film was taken out, and water on the surface was taken up with a filter paper, and the mass We (g) was measured until the decimal point was four. Next, the PVA film was dried in a dryer at 105 ° C for 16 hours, and then the mass Wf (g) was measured to 4 points below the decimal point. From the obtained masses We and Wf, the mass swelling degree of the PVA film was determined by the following formula (VI).

Quality swelling degree (%) = (We / Wf) × 100 (VI)

(7) Optical properties of polarizing film

(i) Translucency with a transmittance of 43.5%

As described in the following examples and comparative examples, in each of the examples and the comparative examples, the five kinds of polarizing films which were produced by changing the iodine concentration in the iodine/potassium iodide/boric acid aqueous solution at the time of stretching in the second stage were as follows. The single transmittance (Y) and the degree of polarization (P) were determined. According to the respective examples or comparative examples, the single transmittance (Y) was taken as the horizontal axis and the degree of polarization (P) was taken as the vertical axis, and 5 The dots are plotted to form an approximate curve, and the value of the degree of polarization (P) when the single transmittance (Y) is 43.5% is obtained from the approximate curve, and this is taken as the "polarization degree of the transmittance of 43.5%". "."

Determination of the monomer transmittance (Y) of "1":

From the center portion in the width direction of the polarizing film, two square samples of 4 cm (stretching direction of uniaxial stretching) × 4 cm (direction perpendicular to the direction of stretching of the uniaxial stretching) were taken. For the samples, the transmittance of the light was measured using a spectrophotometer "V-7100" manufactured by JASCO Corporation. In addition, in the measurement, according to JIS Z 8722 (measurement method of object color), the C-light source is used to perform the visibility correction of the visible light region of the 2 degree field of view. For one sample, the light transmittance at a tilt angle of +45 degrees with respect to the uniaxial stretching direction and the light transmittance at a tilt angle of -45 degrees with respect to the uniaxial stretching direction were measured and determined. The average value of these (Y ₁ ) (%). In the other sample, the light transmittance at the time of +45 degree tilt and the light transmittance at the time of -45 degree tilt were measured in the same manner, and the average value (Y ₂ ) (%) of these was obtained. Then, the obtained Y ₁ and Y ₂ are averaged by the following formula (VII) as the monomer transmittance (Y) (%) of the polarizing film.

Monomer transmittance (Y) (%) = (Y ₁ + Y ₂ ) / 2 (VII)

Determination of the degree of polarization (P) of "2":

In the above-mentioned "1" method for measuring the transmittance (Y) of a single monomer, the light transmittance (Y∥) when the two samples taken are overlapped in parallel with the stretching direction of the uniaxial stretching is measured. (%) and light transmittance (Y⊥) (%) when they overlap with the stretching direction of the uniaxial stretching. The transmittance (Y∥) and (Y⊥) are the same as the above-mentioned "Measurement method of "1" single transmittance (Y)", and the tensile direction of the uniaxial stretching of the sample on the other hand is obtained. The average of the light transmittance at +45 degrees tilt and the light transmittance at -45 degrees tilt. The degree of polarization (P) (%) of the polarizing film was determined from the transmittance (Y∥) and (Y⊥) based on the following formula (VIII).

Polarization (P) (%) = {(Y∥-Y⊥) / (Y∥ + Y⊥)} ^1/2 × 100 (VIII)

(ii) Absorbance (Abs) at a measurement wavelength of 700% at a transmittance of 43.5%

First, as shown in the following examples and comparative examples, in each of the examples and the comparative examples, five kinds of polarizing films (for the iodine concentration in the iodine/potassium iodide/boric acid aqueous solution at the time of stretching in the second stage were changed ( The single transmittance (Y) was in the range of 42 to 44%, and the absorbance (Abs) at a measurement wavelength of 700 nm was determined as follows. In detail, Glan-Taylor稜鏡 is installed in a spectrophotometer "V-7100" manufactured by JASCO Corporation, and a sample of a polarizing film is placed at a position orthogonal to the optical axis (the above "(i) transmittance) 43.5% of the degree of polarization "1" measurement method of the monomer transmittance (Y)", for any one of the two samples taken for each polarizing film), the measurement is made to cause linear polarization by passing the light source through the crucible. The transmittance of light having a wavelength of 380 to 780 nm which penetrates the sample at a wavelength of 700 nm is measured. At this time, the sample is rotated in a plane orthogonal to the optical axis, the transmittance change is measured, and the maximum value T ₀ of the transmittance and the minimum value T _{90 of} the transmittance are obtained, and the sample is calculated according to the following formula (IX). The polarized film was measured for the orthogonal transmittance Tc at a wavelength of 700 nm.

Tc=T ₀ ×T ₉₀ /100 (IX)

Then, using the orthogonal transmittance Tc, the absorbance (Abs) of the polarizing film at a measurement wavelength of 700 nm was calculated from the following formula (X).

Abs=2-logTc (X)

Next, the monomer of the polarizing film is transmitted according to the above-mentioned "(i) measurement method of the partial transmittance (Y) of the polarization degree "1" of the transmissivity of "43" and the absorbance (Abs) of the measurement wavelength of 700 nm. The ratio (Y) is plotted on the horizontal axis, and the absorbance (Abs) at a measurement wavelength of 700 nm is plotted on the vertical axis, and five points corresponding to the above five kinds of polarizing films are plotted to form an approximate straight line, and the approximate straight line is obtained. When the single transmittance (Y) of the polarizing film was 43.5%, the absorbance (A) at a measurement wavelength of 700 nm was used as "absorbance (Abs) at a measurement wavelength of 700 nm at a transmittance of 43.5%".

"Embodiment 1"

(1) Manufacture of PVA-based polymer film

(i) From the T-die, PVA (saponification degree: 99.9 mol%, average polymerization degree: 2400) obtained by saponifying polyvinyl acetate 100 parts by mass, glycerin 12 parts by mass, lauric acid diethanolamine 0.1 parts by mass and a film-forming stock solution having a water volatilization ratio of 66% by mass, and a first drying roll (surface temperature (T ₁ ) of 70 ° C) in a film forming apparatus including a plurality of drying rolls and heat-treating rolls having mutually parallel rotating axes At a peripheral speed (S ₁ ) of 5.0 m/min, a film was formed, and the hot air of 90° C. was sprayed on the first drying roll on the first drying roll at a wind speed of 5 m/sec. Drying until the volatile matter ratio (V ₁ ) is 20% by mass, and then peeling off from the first drying roll, so that the surface and the back surface of any part of the film are in contact with each of the drying rolls, and the second drying roll is located directly in front of the heat treatment roll. After the last drying roll was further dried, it was peeled off from the last drying roll. At this time, the average value (T ₂ ) of the surface temperatures of the respective drying rolls from the second drying roll to the last drying roll was 61 °C. Further, since the volatile content of the film when the final drying roller peeling (V ₂₎ 8% by mass. After heat treatment at a heat treatment roll having a surface temperature of 105 ° C, the film was wound into a roll to obtain a PVA film (thickness: 75 μm, width: 3.3 m, volatile matter: 3% by mass).

In the first embodiment, the ratio (S ₂ /S ₁ ) of the peripheral speed (S ₂ ) of the second drying roller to the peripheral speed (S ₁ ) of the first drying roller is set to 1.025, and the relative The ratio (S _L /S ₁ ) of the peripheral speed (S _L ) of the drying roller at the end of the peripheral speed (S ₁ ) of the first drying roll was set to 0.982. Further, T _{1 → 2} of the above formula (I) is calculated to be 67. The above film forming condition system is shown in Table 1 below.

(ii) The crystal long period, crystal thickness, and amorphous thickness of the PVA film obtained in the above (i) in water; the retardation value and the mass swelling degree are measured by the above method, as shown in Table 2 below.

(2) Manufacture of polarizing film

(i) A test piece having a flow direction (MD) × width direction (TD) = 10 cm × 12 cm from the center portion in the width direction (TD) of the PVA film obtained in the above (1), and the flow direction of the test piece Both ends are fixed by a stretching jig so that the size of the stretched portion becomes a flow direction (MD) × a width direction (TD) = 6 cm × 12 cm, and is pulled at 12 cm/min during immersion in water at a temperature of 30 °C. When the stretching speed is uniaxially stretched (first stage stretching) in the flow direction (MD) to 1.5 times the original length, the concentration is 0.028% by mass of iodine and 1% by mass of potassium iodide, and 1% by mass of boric acid. While immersed in an iodine/potassium iodide/boric acid aqueous solution at a temperature of 30 ° C, the film was uniaxially stretched in the flow direction (MD) at a stretching speed of 12 cm/min (2nd stretch) until the original length was 2.25 times, and then, While immersing in a boric acid/potassium iodide aqueous solution containing a concentration of 4% by mass of boric acid and 4% by mass of potassium iodide at a temperature of 53° C., uniaxially stretching in a flow direction (MD) at a tensile speed of 12 cm/min (third) The film was stretched until it was 5.8 times the original length, and then dried in a dryer at 60 ° C for 4 minutes to prepare a polarizing film.

(ii) In the above (i), except that the concentration of iodine in the iodine/potassium iodide/boric acid aqueous solution at a temperature of 30 ° C at the time of stretching in the second stage is changed from 0.028 mass% to 0.03 mass%, The same operation [the stretching speed at each stretching stage was 12 cm/min as in the above (i)], and a polarizing film was produced.

(iii) In the above (ii), except that the concentration of iodine in the iodine/potassium iodide/boric acid aqueous solution at a temperature of 30 ° C at the time of stretching in the second stage is changed from 0.028 mass% to 0.032 mass%, The same operation [the stretching speed in each stretching stage is 12 cm/min as in the above (i)], and is manufactured. Polarized film.

(iv) In the above (i), except that the concentration of iodine in the iodine/potassium iodide/boric acid aqueous solution at a temperature of 30 ° C at the time of stretching in the second stage is changed from 0.028 mass% to 0.034 mass%, In the same operation, [the stretching speed at each stretching stage was 12 cm/min as in the above (i)] to produce a polarizing film.

(i) In the above (i), except that the concentration of iodine in the iodine/potassium iodide/boric acid aqueous solution at a temperature of 30 ° C at the time of stretching in the second stage is changed from 0.028 mass% to 0.036 mass%, In the same operation, [the stretching speed at each stretching stage was 12 cm/min as in the above (i)] to produce a polarizing film.

(vi) using the five kinds of polarizing films manufactured by the above (i) to (v), in the item "(7) Optical properties of polarizing film (i) Translucency of 43.5% transmittance", by the aforementioned method The degree of polarization was measured to be 99.9%. Further, in the item "(7) Optical performance of polarizing film (ii) absorbance (Abs) at a measuring wavelength of 700 nm of a transmittance of 43.5%", the absorbance (Abs) was measured by the above method to be 3.2. These results are shown in Table 2 below.

<<Examples 2 to 7>>

In the first embodiment, the PVA film and the polarizing film were produced in the same manner as in the above (1) and (2) except that the film forming conditions in the production of the PVA film were changed to those described in the following Table 1.

Using the produced polarizing film, "(7) Polarized film optical properties (i) Translucency: 43.5% of the degree of polarization" and "(7) Optical properties of the polarizing film (ii) at a transmittance of 43.5% of the measured wavelength of 700 nm In each item of the absorbance (Abs), the degree of polarization and light absorption are measured by the aforementioned method. Degree (Abs). The results are shown in Table 2 below.

Comparative Example 1~6

In the first embodiment, the film forming conditions in the production of the PVA film were changed to those described in the following Table 1, and the PVA film and the polarizing film were produced in the same manner as in the above (1) and (2).

Using the produced polarizing film, "(7) Polarized film optical properties (i) Translucency: 43.5% of the degree of polarization" and "(7) Optical properties of the polarizing film (ii) at a transmittance of 43.5% of the measured wavelength of 700 nm In each item of the absorbance (Abs), the degree of polarization and the absorbance (Abs) were measured by the methods described above. The results are shown in Table 2 below.

Comparative Example 7

In the first embodiment, when the film forming conditions in the production of the PVA film were changed to those described in the following Table 1, the first drying roll became poor in drying, and the film could not be peeled off from the first drying roll to cause breakage. The volatile matter of the fractured film was measured to be 31% by mass.

[Industrial availability]

The PVA-based polymer film of the present invention has a crystal long period of 14.5 to 16.0 nm in water, and when the PVA-based polymer film is used as a raw material, a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization can be produced. Therefore, the PVA-based polymer film is extremely useful as an initial film for producing a polarizing film, and then the production method of the present invention is useful as a method for smoothly and continuously producing the PVA-based polymer film of the present invention.

Claims (3)

A method for producing a polarizing film which is obtained by dyeing a polyvinyl alcohol-based polymer film having a crystal long period of 14.5 to 16.0 nm in water, and performing one-axis stretching, fixing treatment, and drying treatment. A polarizing plate to which a protective film is attached to a polarizing film manufactured by the manufacturing method of claim 1. A method of producing a polarizing plate, wherein a protective film is bonded to a polarizing film manufactured by the method of claim 1 of the present invention.